1. Field of the Invention
Methods and apparatuses consistent with the present invention relate to a package of a light emitting diode (LED) used for generally backlight units of liquid crystal displays (LCD) and lightings and a fabrication method thereof.
2. Description of the Related Art
Since LEDs have many advantages such as a long life span and low power consumption, they are being used in a variety of fields including electronics and advertising. Recently, there have been attempts to use LEDs as backlight units in LCD devices, and it is expected that the use of LEDs in indoor and outdoor lighting systems will become wide spread. There is an increasing demand for LED packages with a small size and which can efficiently dissipate heat.
LEDs used in backlight units for LCDs or in lighting apparatuses require high power consumption. However, when the temperature rises, the performance of LEDs exponentially decays. Therefore, thermal management of LED packages is important.
FIG. 1 illustrates a cross-sectional view of a conventional LED package. As illustrated in FIG. 1, the LED package includes an LED 1, a heat sink member 2 on which the LED 1 is disposed, leads 3 and 3′, wires 4 and 4′ for electrically connecting the LED 1 to the leads 3 and 3′, and a body 5 for enclosing the heat sink member 2 and the leads 3 and 3′ therein.
The heat sink member 2 is exposed on the bottom surface thereof and is covered with an insulating layer 6 on the top surface thereof. The LED 1 is bonded at the center portion of the insulating layer 6 by an adhesive 7 and first ends of each of the leads 3 and 3′ are arranged on the sides of the insulation layer 6. The second ends of the leads 3 and 3′ project from the sides of the body 5 and are exposed. The wires 4 and 4′ connect the LED 1 to the first ends of the leads 3 and 3′. A cap (not shown) can be disposed on the top of the body 5 for sealing the LED 1.
The conventional LED package as described above is mounted on a board 10 such that the second ends of the leads 3 and 3′ are soldered to pads 11 and 11′, respectively, provided on the board 10. Further, since solder 12 is disposed between the heat sink member 2 of the LED package and the board 10, heat generated by the LED 1 can be released via the heat sink member 2, the solder 12 and the board 10.
However, conventional LED packages, such as shown in FIG. 1, have long heat transfer paths (e.g: LED→insulating layer→heat sinking member→solder→board). Further, since the heat transfer path includes many different materials, the heat sinking capability decreases due to an increase in thermal resistance. Accordingly, a conventional LED package such as described above is not suitable for high power LEDs.
Thermal resistance Rth is expressed by the following equation: Rth=L/(k*A). According to this equation, the thermal resistance Rth decreases as thickness becomes smaller, that is, the heat transfer path L becomes shorter, and the heat transmittance k and the heat sinking area A become larger. However, since a conventional LED has contacts formed between different materials and the heat transfer path L is long, thermal resistance is high in a conventional LED package.
When heat dissipation performance of an LED package is not good, the life span of the LED may be reduced and fatal damage may be caused to the system employing the LED package because the peripheral parts of the system may deteriorated or be thermally deformed.
Further, since the parts of a conventional LED package (e.g. the package body, the leads, and the pads) are formed separately, a method of fabricating the LED package and the structure of the LED package are complicated.